Sri Aurobindo
Letters of Sri Aurobindo
Volume III - Part 3
I don’t think it is at all owing to the suggestion from what I wrote in the letter that you got the experience [of a deep spiritual peace]. The fundamental reason of these things does not belong to the surface, it is in the depths – or on the heights, at any rate, in the inner being behind the veil of the frontal consciousness. The actual occasional cause of the spiritual experience,– the match that sets the fire, so to say,– may be something very slight and looking accidental on the surface, a chance word or happening or something else quite fortuitous in its appearance. The person also through whom it comes may seem very much like a fortuitous instrument. It is true that this is only in appearance; for things slight and seemingly fortuitous have a reason for happening as they do, but that reason too is not on the surface.
As for the experience itself it takes up the movement which had started in you a long time ago and was interrupted by the vital upheaval that brought you so much trouble and struggle. Only, there has been since a widening of the consciousness and a step forward which made this form of the experience possible. At that time you had not much appreciation for calm and peace – you hankered only after bhakti and Ananda. But calm, peace, shanti are the necessary basis for any establishment of other things. Otherwise there is no solid foundation in the consciousness; if there is only unrest and movement, bhakti, Ananda and everything else can only come and go in starts and fits and find no ground to live on. It must, however, be not a mere mental quiet, but the deep spiritual peace of the shantimaya Shiva. It was this that touched you (descending through the head) in this experience. For the rest it is a resumption of the piercing of the veil, the beginning of the power of inner experience as opposed to the lesser experiences of the surface, the opening of the inner being, which is necessary for bringing the Yogic consciousness. A certain amount of vital purification has taken place which made the resumption of this kind of experience possible.
You certainly need not be afraid of going into unconsciousness, for it is not unconsciousness that you would go into, but simply the inner consciousness,– that going quite inward which 
is the result of intense dhyāna and the beginning of a certain kind of samādhi.